The muscles of and surrounding the anal canal are critical to normal bowel and bladder function. The anal canal will be considered to include the tissue from the anal verge, where the anal canal opens to outside of the body, to the recto-anal juncture.
When the muscles of the anal canal are weakened or damaged, as a result of disease, trauma, neuropathy, post-surgical injury, and the like, a variety of disorders such as constipation, diarrhea, incontinence, hemorrhoids, or rectal prolapse may occur. Some of these muscles are innervated by the somatic nervous system and thus the possibility exists that they may be rehabilitated by means of biofeedback techniques which help exercise or retrain these muscles. Nevertheless, the proper functioning of these muscles is not well understood nor easily studied. As a consequence, it is difficult to diagnose the cause of a particular disorder or to identify the muscles involved and thus to determine the proper treatment and the likelihood of successful rehabilitation.
Myographic probes for insertion in the anal canal which provide general information as to the muscle activity in this region, have produced disappointing results as far as diagnosing various disorders of the anal canal.
One promising technique for studying the muscles of the anal canal is digital subtraction defecography, a radiographic technique which can produce multiple x-ray images of these muscles separated by an interval of about 1 to 1 1/2 seconds. By studying the sequence of these images it is thought that the coordination of the various muscles of the anal canal and the muscles in its proximity (together, "the anal canal group") may be better understood to establish a guide for treatment and a basis for accurate prognosis. It is possible that early diagnosis of the functional disorder of the muscles of the anal canal can suggest preventative measures to arrest or reverse this disorder and thereby to avoid further and more serious organic damage.